A new market that many liquid crystal display (LCD) manufacturers are struggling to break into is the 3D display market, particularly the market of 3D displays that do not require viewers to wear special eyewear to view 3D effects. Current 3D display technology is split into two major branches: spatial differentiation and temporal differentiation. Both technologies operate on the principle of splitting the image signal into two independent signals sent individually to the right eye and the left eye, without requiring extra eyewear to filter the signals. Temporal differentiation is gaining the attention of designers, because it does not reduce resolution and can provide highly refined 3D effects. However, temporal differentiation is limited in that the time required for the LCD to achieve a stable state is relatively long, which makes it a challenge to provide a high brightness image.
Simply speaking, in spatial differentiation, after a power supply turns on, the display panel will set up a micro-optical parallax grate, which is shaped similar to a wooden fence, and has an operating principle similar to polarized 3D glasses. The light rays representing the image are bent by the grate, and the right eye and the left eye see alternating pixels in the same row. The human brain then forms a 3D image from the two different images seen. One disadvantage of spatial differentiation is that it reduces image resolution, because the right eye and the left eye only see one half of the image. For example, if the display panel has a resolution of 800×600 pixels, each eye will see a 400×600 pixel image. The 3D image combined in the brain will also have the reduced resolution of 400×600 pixels.
The following is a description of the principle of temporal differentiation. FIG. 1 is a diagram of a display panel 1 according to the prior art, where each square represents one image pixel. FIG. 2 is a diagram of a backlight module 2 at an underside of the display panel 1 of FIG. 1. The backlight module 2 comprises light sources 21, 22 on its opposite sides, and a light guide panel 23.
FIG. 3 is a schematic top view of the display panel 1 and the backlight module 2. A micro-lens 5 is positioned between the display panel 1 and the backlight module 2, and is used for directing light rays to the left eye and the right eye, such that the left eye and the right eye can receive individual parallax images. Because the light sources 21, 22 of the backlight module 2 have a special angular arrangement, if the light source 22 is ON, the light rays emitted from the light source 22 will be incident upon the micro-lens 5 through total reflection in the light guide panel 23. The micro-lens 5 can be formed of a convex lens and a prism. As shown in FIG. 3, one side of the micro-lens 5 comprises a plurality of arced faces, and an opposing side of the micro-lens 5 comprises a plurality of corresponding refractive faces shaped like a row of saw teeth. Thus, the micro-lens 5 directs the light rays from the light source 22 and reflected off light guide panel 23 at a specific angle toward the left eye, where the light rays converge. As a result, the left eye receives the left eye parallax image. The same applies to the light source 21 and the right eye signal and parallax image.
FIG. 4 is a sequence diagram showing a conventional method of controlling the display panel 1 of FIG. 1 and the light sources 21, 22 of the backlight module 2 of FIG. 2. Because the human brain retains images received through the eyes for approximately 16.67 ms, the brain can form a 3D image from the images received if the right eye signal and the left eye signal are sent to the right eye and the left eye of the observer, such that the right eye and the left eye receive the right eye parallax image and the left eye parallax image, respectively, within 16.67 ms. In other words, the frame time distributed to the left eye signal and the right eye signal is only 8.3 ms each.
In the sequence diagram of FIG. 4, the left eye signal is sent first, and the right eye signal is sent second. For example, the approximate time required for sending the image from the 1st scan line to the last, e.g., 320th, scan line is 3 ms. After the data corresponding to the 320th scan line has been sent, the entire display panel 1 must wait for the liquid crystals to settle, for approximately 4 ms, before the light source 22 of the backlight module 2 can be turned ON, so as to allow the left eye to receive the left eye parallax image. After the light source 22 turns OFF, the process is repeated for displaying the right eye parallax image. To prevent the right eye parallax image and the left eye parallax image from interfering with each other, and thus degrading the desired 3D visual effect, the light sources 21, 22 must wait for the data of the entire display panel 1 to finish updating (i.e., respond to the received image data) before they can be turned ON. Then, the light sources must be turned OFF before the next parallax image begins updating. In other words, the light source 22 must be turned OFF before sending the right eye signal. Likewise, the light source 21 must be turned OFF before updating the next (left eye) parallax image. Hence, the proportion of time that the light sources 21, 22 are ON for displaying the parallax images compared to the time frame period is quite small. For example, after deducting 3 ms required for sending the image signal and 4 ms required for allowing the liquid crystals to respond to the received image signal, the amount of time the light sources 21, 22 are actually ON is only about 1.3 ms. Within one period, the proportion is only about 1.3/8.3, which means that the image brightness will be insufficient. Thus, high power light sources must be used to provide the needed brightness within the short period of time, which causes a disadvantage in power consumption.